To save yourself wiring trouble you can get one that has the controls right on the unit, that way it is very simple to install and hookup to the pre-wiring. The pre configured setups do not use the duct work, from that aspect they are a standalone unit. You may also want to consider getting a low profile unit if this is on the front of a 5th.
I did this last year and here is what I found out, pre-wired is electric to the point of install, no wiring back to the thermostat or pre-configured path for you to add a second thermostat in the room (hence why controls on the unit are an easier choice).

Hi there! I can't speak much to the technical aspects, but my 5th wheel has a standalone unit on the front. The fan on my unit is either on or off... no auto selection, and no real thermostat. If I ever replaced it, I would look for something quieter that had an actual thermostat. Mine is a "Coleman Mach"...not sure of the model. Only has the following settings: Low and High Fan, Low and High Cool. Has a colder/hotter knob that does seem to cycle the a/c... but the fan itself never shuts off.